The present invention relates to methods and apparatus for plating a conductive material on a semiconductor substrate. More particularly, the present invention is directed to xe2x80x9cproximity platingxe2x80x9d methods and apparatus for plating the conductive material on the semiconductor substrate. The substrate is plated with the conductive material as the pad and/or blade type objects are rotated in close proximity to the substrate.
A conventional process step in the manufacturing of integrated circuits and devices involves plating a conductive layer on a semiconductor substrate. Plating the substrate with the conductive material over a seed layer has important and broad application in the semiconductor industry. Traditionally, aluminum and other metals are deposited as one of many conductive layers that make up a semiconductor chip. However, in recent times, there is great interest in copper deposition for interconnects on semiconductor chips, because, compared to aluminum, copper reduces electrical resistance and allows semiconductor chips to run faster with less heat generation, resulting in a significant gain in chip capacity and efficiency.
Typically, the semiconductor substrate has been previously etched and contains many holes and/or trenches on its surface. One goal of plating is to uniformly fill the holes and trenches with the conductive material.
However, as known in the art, conventional plating methods result in xe2x80x9cdishingxe2x80x9d or non-planar deposition during the plating process. In FIG. 1A, a barrier layer 4 and a seed layer 6 is disposed upon a substrate 2, where a section of the substrate 2 includes a trench 12. After forming the barrier layer 4 and the seed layer 6, a conductive layer 8 is plated on top of the seed layer 6. Because the trench 12 may be relatively large, a recess 10 is formed thereon and dishing results.
For small features with sub-micron size dimensions, existence of voids in the deposited conductive layer is a common problem. In FIG. 1B, such a void 14 is formed near the bottom of a narrow hole 16. It is well known that the existence of such voids in the deposited conductive layer results in defective devices with poor performance. Accordingly, the present invention provides a more accurate, fast, cost effective, and reliable manner of applying the conductive material to the semiconductor substrate.
It is an object of the present invention to provide methods and apparatus that deposit a conductive material on a substrate with the pad or blade type objects rotating in a circular manner.
It is another object of the present invention to provide methods and apparatus that deposit a conductive material on a substrate while eliminating/reducing dishing and voids.
It is yet another object of the present invention to provide methods and apparatus that deposit a conductive material on a substrate using novel pad-anode or blade-anode assemblies.
These and other objects of the present invention are obtained by providing methods and apparatus for depositing a conductive material from an electrolyte solution to the substrate. This is achieved by providing pad or blade type objects mounted on cylindrical anodes or rollers and applying the conductive material to the substrate using the electrolyte solution disposed on or through the pads or on the blades.
An apparatus that performs such plating includes anodes and a cathode workpiece that are in close proximity of each other. The pad or blade type objects mounted on the cylindrical anodes or rollers rotate about a first axis and the workpiece may be stationary or rotate about a second axis, and metal from the electrolyte solution is deposited on the workpiece when a potential difference is applied between the workpiece and the anode.
Alternatively, the plating apparatus may include an anode plate spaced apart from the cathode workpiece. Upon application of power to the anode plate and the cathode workpiece, the electrolyte solution disposed in the plating apparatus is used to deposit the conductive material on the workpiece surface using cylindrical rollers having the pad or blade type objects.
Further, in another embodiment, the plating apparatus may include an anode plate spaced apart from cylindrical cathodes having conductive pads or blades. Upon application of power to the anode plate and the cathodes and upon rotating the cathodes in a circular direction, the conductive pads or blades make electric contact to the workpiece surface rendering it cathodic with respect to the anode plate, and metal from an electrolyte solution is deposited on the same surface.